1. Field of the Invention
This invention relates to improvements in branch pipe systems, and more particularly in the pipe outlet invention and fittings disclosed and claimed in my U.S. Pat. No. 4,541,656 issued Sept. 17, 1985, and entitled CAST METAL OUTLET FITTING.
2. Description of the Related Art
In the patent above identified a cast metal outlet fitting having at one end a fishmouth configuration, was secured to a distribution pipe by positioning the fitting over a hole in the pipe, with the use of criss-crossed positioning marks scribed on the pipe and cooperable positioning lugs on the outlet fitting. By such an arrangement a precise location of the the fitting over the hole was made possible; thereafter, welding material was applied at the junction of the fishmouth configuration and pipe so as to form both a mechanical connection and a permanent leak-resistant seal between the two parts. Preferably the other end of the fitting was threaded in order to accept a coupling (not shown) enabling the attachment of additional pipe sections thereto.
While the disclosed arrangement operated in a satisfactory manner and provided reliable results as far as maintaining the integrity of the connection and seal between the pipe and fitting was concerned, the use of welding for establishing the connection had distinct drawbacks.
In particular, in many installations such as laboratories and the like, the presence of combustible gases made use of welding equipment prohibitive, due to the danger of explosion. In the case of "clean rooms" which are employed to assemble and test certain types of electronic, mechanical, and medical equipment, welding would contaminate the clean environment. In addition, welding equipment was generally bulky and heavy to transport, and required a suitable source of electricity for operation. In some instances, as where a new building was under construction, electric power was not readily available, which required that a portable source be employed.
Finally, there existed the need for on-site skilled personnel, usually certified welders, in order to perform the necessary work. All of the above factors contributed to increased costs and inflexibility as to installation. Since much of the installation had to be accomplished "on site" where the distribution system was to be employed, it was usually not feasible to pre-assemble the required piping networks at the factory and then transport them to the particular facility for installation.
An article "How To Weld Pipe, Comprehensive Instructions for Cutting and Welding Pipe, and for Fabricating Pipe Fittings", published by the Linde Air Products Company, Unit of Union Carbide and Carbon Corporation, New York, N.Y., 1943, page 18, FIG. 43, illustrates a method of applying markings to a distribution pipe and outlet fitting, employing paper templates, to facilitate accurate positioning of the fitting prior to welding. This arrangement was solely applicable to welded or soldered joints.
A number of patented distribution and coupling arrangements have been devised in the past. As examples, reference is made to U.S. Pat. No. 1,801,171 illustrating the use of solder between a male and female member in order to provide the desired mechanical retention and pressure-resistant seal. U.S. Pat. No. 1,823,549 illustrates various types of T-couplings employing solder to assemble the various parts. Welded couplings are illustrated in U.S. Pat. Nos. 1,936,805; 1,966,403; 2,015,246; 2,463,006; 2,915,324; and 3,516,692.
A pipe fitting incorporating a sealing O-ring between a coupling and plug is illustrated in U.S. Pat. No. 2,954,604. The O-ring was concealed in a recess on the interior surface of a collar associated with the plug. The disclosed construction was intended for use with hydraulic pressure systems.